The present invention provides an orthotic device incorporating a shape memory alloy element as the actuation means. Generally, the shape memory of an alloy involves a transformation in the metal from a low temperature disorganized crystal structure to a high temperature highly ordered crystal structure. The phase transformation occurs at a specific temperature. Thus, if a metal has been "programmed" with a certain memory shape and is deformed at a low temperature, the metal will recover its memory shape when heated above the transition temperature. A material having such properties is particularly useful in a diverse range of applications. One such application is illustrated in U.S. Pat. No. 4,553,393. In this document, Ruoff discloses an actuator incorporating a shape memory alloy. The actuator provides torque or force directly to a load to eliminate the use of motors or transmissions, etc. conventionally used to achieve the same result.
Further, Jamieson, in U.S. Pat. No. 4,665,334 discloses a rotary stepping device which includes a shape memory metal as a main drive unit for a motor. The memory metal provides drive motion to a spring clutch. The clutch is positioned about a shaft and when the metal is actuated, the clutch tightens effecting rotation of a shaft of the motor. Although useful devices, the prior art is not directed to medical applications. The present invention permits a quadriplegic or similarly disabled person to regain grasping function. By employing a shape memory alloy in an orthotic device, the user can simply and expediently grasp and release an object without any undue discomfort or with the use of a complicated apparatus.